Matching exercises not working

There are problems with the matching exercises - the ones where a line should be drawn betwen two selected items.

Recently there have been more and more faults I believe (also see other posts by others).

Sometime a line is not drawn, sometimes the buttons don't even turn black when selected.

For example, I have just tried the Upper Intermediate Lesson - Alcoholic Attitudes.  In IE the buttons select but no line is drawn.  In firefox the first question was ok, but in the second no buttons could be selected.